The present invention is generally directed to a belt type abrading machine such as a grinder or sander, or other belt using machine; and, is more particularly directed to a belt tracking mechanism for such a machine.
Belt grinders or sanders of the general type having a belt drive pulley, at least one driven or idler pulley and an endless abrasive or other belt trained over the pulleys are old in the art, as evidenced by U.S. Pat. Nos. 3,497,336 and 4,294,044. During the operation of such a machine, it is desirable that the belt track properly over the pulleys, that is, that it maintain a position substantially laterally centered on the belt engaging faces of the pulleys. However, slight alignment errors in the relation of the axes of the pulleys to one another or slight variations in the lengths of the edges of the belt can cause the belt to move off track by shifting laterally to one side or the other from the desired centered position. In some instances, the belt may run completely off of the pulleys or rub against a wall or other structure located adjacent one or both of the pulleys or the belt.
To allow for correction of the running path of the belt, it has been common practice in belt abrading machines to provide a means for adjusting the inclination of an idler pulley axis relative to the drive pulley axis. Such adjustment means have however tended to pose various problems of their own, including being of a complex, expensive construction and being difficult to operate or fine tune.
It is an object of the present invention to provide a simplified, inexpensive, and easy to operate adjustable belt tracking mechanism for belt type abrading machines and the like. The invention provides a support member for the idler pulley having a threaded stud attached thereto and an adjustment knob threadably engaged with the stud such that the stud and adjustment knob serve to both pivotally connect the support member to the machine frame for movement about an axis generally parallel to the pulley axes, to allow for variance in the spacing between the axes of the idler and drive pulleys, and to also connect the support member to the frame in such a way that the support member may pivot relative to the frame about an axis or hinge line located in a plane perpendicular to the idler pulley axis to change the inclination of the idler pulley axis relative to the drive pulley axis, with rotation of the adjustment knob effecting such change in inclination.
The present invention resides in a belt type abrading machine having a frame, a drive pulley mounted on the frame for rotation about an axis fixed relative to the frame, an idler pulley, an endless belt abrasive or otherwise trained over the drive pulley and the idler pulley, and a novel means for connecting the idler pulley to the frame whereby the spacing between the axes of the two pulleys may be varied, the idler pulley axis being urged away from the drive pulley axis by a spring to tension the belt, in conjunction with the a tracking adjustment whereby the inclination of the idler pulley axis relative to the drive pulley axis may be adjusted to bring the belt to a condition of tracking properly over the two pulleys while the machine is running. The frame of the machine can be oriented such that the drive and idler pulleys are aligned either in a horizontal or vertical configuration.
The invention more particularly resides in an idler pulley support member being provided for supporting the idler pulley for rotation about an axis fixed relative to the support member. The idler pulley support member is in turn itself connected to the frame by a threaded stud and an adjustment knob threadably coupled with the stud. The adjustment knob is rotatably engaged with an aperture in the frame such that the support member is supported for movement relative to the frame about the axis of the stud which extends generally parallel to the pulley axes to allow the idler pulley, as a result of such rotation of the support member relative to the frame and about the axis of the threaded stud, to be moved toward or away from the drive pulley to loosen or tighten the belt with respect to the pulleys, the support member being further biased by a spring in the belt tightening direction so that the belt will normally be tensioned. The adjustment knob and threaded stud, together facilitate an angular adjustment of the support member relative to the frame about a tracking adjustment axis located in a plane generally perpendicular to the idler pulley axis. The support member and the frame engage one another along the tracking adjustment axis and are held in such engagement by the moments exerted on the support member by the belt and the spring.